21380720 has 20 divisors (see below), whose sum is σ = 49710360. Its totient is φ = 8552256.

The previous prime is 21380693. The next prime is 21380729. The reversal of 21380720 is 2708312.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21380729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133550 + ... + 133709.

It is an arithmetic number, because the mean of its divisors is an integer number (2485518).

Almost surely, 2^21380720 is an apocalyptic number.

21380720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21380720 is an abundant number, since it is smaller than the sum of its proper divisors (28329640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21380720 is a wasteful number, since it uses less digits than its factorization.

21380720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 267272 (or 267266 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21380720 is about 4623.9290651999. The cubic root of 21380720 is about 277.5497083801.

The spelling of 21380720 in words is "twenty-one million, three hundred eighty thousand, seven hundred twenty".